The present invention relates to a stereoscopic endoscope which allows an observer to view a three-diminsional image of an object under test.
A stereoscopic endoscope is used to observe an object or cavity internal to a machine or the human body. Examples of rigid type stereoscopic endoscopes are disclosed in, for example, U.S. Pat. No. 4,364,629 and Japanese Laid Open Publication Hei. 6-194581. In these examples, the stereoscopic endoscopes have an insertion portion which includes an objective lens for forming an image of the object and a relay lens for transmitting the light to an exit pupil of the insertion portion. The stereoscopic endoscopes also include an observing portion, which includes an optical device for splitting the light at the exit pupil and directing the split light beams to a left and right optical imaging system, through which an observer would view the a three-dimensional image of the object.
However, if the optical device for splitting the light beam is not positioned correctly, the three-dimensional effect of the image may be reduced, thereby reducing the effectiveness of the endoscope. Further, even if the optical device for splitting the light beam is positioned correctly for an object located near to the insertion portion of the endoscope, the three-dimensional effect of an image of an object located far away from the insertion point of the endoscope may be reduced. This also reduces the effectiveness of the endoscope.
In conventional stereoscopic endoscopes, the three-dimensional image is viewed directly, using eyepiece lenses, or indirectly using an imaging device such as a CCD, and a video processor. Use of an imaging device allows the images to be viewed by many people, through the use of a monitor and special viewing glasses. However, this requires extra hardware and elaborate image processing. In a direct viewing endoscope, the image may be viewed easily and quickly through the eyepiece lenses, but by only one person at a time. Thus, extra time will be required if many people are to view the image.
Further, in a conventional stereoscopic endoscope that employs the imaging devices, one imaging device is used with each optical system, thereby increasing the cost of manufacturing the cost of the endosocope.
In conventional stereoscopic endoscopes the optical device for splitting the light beam uses a series of reflective surfaces in order to properly split the light beam. Therefore, the positional relationship between the various reflective surfaces must be set precisely. Further, in order properly position all of the reflective surfaces, the size of the endoscope must be made large, thereby reducing the effectiveness of the endoscope. Furthermore, the number of parts required to manufacture the endoscope is increased.
In a conventional stereoscopic endoscope, light is provided to illuminate the object by using a separate light source and an optical guide. The optical guide is housed in the insertion portion of the stereoscopic endoscope, and is parallel to the optical axis of optical system used for viewing the image. This results in the diameter of the insertion portion being large, and therefore the insertion portion cannot be as easily inserted into the cavity.